Conventionally, there has been known a printer unit in which the printing object mediums are accommodated in a laminated manner in the accommodating portion thereof in order to supply the printing object medium to the printing means by rotating the supply roller kept in contact with the printing object medium. When printing is executed, the supply roller is rotated to supply the recording object medium. Thus, if the printer unit continues to be used, such a fault as paper feeding trouble is generated because the supply roller is deteriorated. To eliminate such a fault, the supply roller needs to be replaced, however a conventional printer unit takes much time and labor for the replacement work of the supply roller because the supply roller is incorporated within the printer unit main body.
As a disclosure for solving this kind of the problem, an invention described in Japanese Patent Application Laid-Open No. 2001-294335 has been well known. The Japanese Patent Application Laid-Open No. 2001-294335 has described an invention relating to an image forming apparatus in which a supply unit including the supply roller is attached detachably. That is, the image forming apparatus described in the Japanese Patent Application Laid-Open No. 2001-294335 enables the supply unit to be replaced when the supply roller is deteriorated and needs to be replaced. Consequently, related consumption components can be replaced without disassembling the image forming apparatus entirely.
However, even when a consumption component (for example, a supply roller) is deteriorated in the image forming apparatus described in the Japanese Patent Application Laid-Open No. 2001-294335, the entire supply unit needs to be replaced. That is, in case of the image forming apparatus described in the Japanese Patent Application Laid-Open No. 2001-294335, even if a separation feeding roller or the like constituting the supply unit is still usable, the entire supply unit is replaced, which is a large waste. Additionally, because the entire supply unit is replaced, the cost relating to the replacement component becomes higher than a case of replacing only the supply roller.
When replacing the supply roller in the image forming apparatus described in the Japanese Patent Application Laid-Open No. 2001-294335, disassembly work of the supply unit and reassembly work of the supply unit after the supply roller is replaced are necessary because the supply roller is assembled into the supply unit. In this case, other components than the supply roller of the supply unit need to be disassembled, resulting in that extremely much time and labor are required for the replacement work of the supply roller. In this point, because the supply unit itself is constructed in a relatively complicated structure, time and labor required for the replacement work of the supply roller increase. Further, because the supply unit needs to be reassembled after the supply roller is replaced, if the assembly work is not carried out accurately, the image forming apparatus may not operate properly. Particularly, because other components than the supply roller are disassembled upon replacement work, a fault (a fault caused by the replacement work is called a secondary fault) may occur in any component which operates properly before the replacement.